The Ultimate Boxing HIIT Class. Designed by Professional Boxing and S&C Coach ‘The Burf’, Berserker is designed to take you to places other HIIT classes simply can’t. BERSERKER isn’t so much a class…More a challenge to both physical and mental endurance. Think army assault course where every challenge sits immediately behind the next…No respite! Book your Berserker class today but be warned…It’s not for the feint hearted!!